The (n,2n) and (n,3n) Reactions of Lead, A Potential Neutron Amplifier for Fusion Blankets

Complete evaluations of the (n,2n) and (n,3n) reaction cross sections were carried out for the stable isotopes of lead and for natural lead, that element being a potential neutron amplifier for fusion blankets. The method of computation used is based on the Segev simple formalism for compound nucleus decay without branching. This method, which was already checked for ²⁰⁴Pb, was used for cross-section computation for all other stable lead isotopes. From these results, evaluated cross sections could be derived for natural lead. The results of the evaluations were in good agreement with experimental data. Small discrepancies with the measured data for ²⁰⁴Pb, ²⁰⁷Pb, and ²⁰⁸Pb at low excitation energies above threshold are overcome through the introduction of an “effective” threshold energy slightly higher than the real one. This single correction is sufficient for matching the shape of the evaluated curves to the measured data over the entire energy range for the second neutron emission.